1. Field of the Invention
The present invention relates to a technology allowing a viewer to view a video image displayed on a display device through an eyeglass device. More particularly, the present invention relates to a technology with the eyeglass device to switchingly provide the video image on a display for a viewer.
2. Description of the Background Art
Video systems provided with a display device configured to display a video image and an eyeglass device configured to assist a viewer in viewing the video image displayed on the display device are used, for example, to provide a three-dimensional image. Exemplary video systems are disclosed in Japanese Patent Application Laid-open No. H11-98538 and Japanese Patent Application Laid-open No. 2000-36969.
Japanese Patent Application Laid-open Nos. H11-98538 and 2000-36969 disclose technologies for communication between a display device and an eyeglass device. Japanese Patent Application Laid-open No. H11-98538 discloses a technology resolving a problem on a temporal interruption in communication between the display device and the eyeglass device. The eyeglass device disclosed in Japanese Patent Application Laid-open No. H11-98538 generates an internal signal based on a signal from the display device that represents switching of video frames. The eyeglass device controls opening and closing of liquid crystal shutters based on the generated internal signal. As a result, the liquid crystal shutters are favorably controlled even if there is a temporal failure in the signal communication. Thus, a problem resulting from the temporal failure in the signal communication (such as failure to provide a three-dimensional image for a viewer or image flickering) can be reduced. In addition, the eyeglass device disclosed in Japanese Patent Application Laid-open No. H11-98538 is configured to control the liquid crystal shutters using a signal having a plurality of clocks that indicate switching between a video image for the left eye and a video image for the right eye.
Japanese Patent Application Laid-open No. 2000-36969 proposes switching between opening and closing of left and right shutters of an eyeglass device during a non-display period in a subfield. According to the technology disclosed in Japanese Patent Application Laid-open No. 2000-36969, a viewer may view three-dimensional images even if the viewer uses an eyeglass device with so slow response rate that switching of shutter between opening and closing at the same time as a beginning of a subfield may result in blocking light from a plasma display panel (PDP).
The eyeglass devices disclosed in Japanese Patent Application Laid-open Nos. H11-98538 and 2000-36969 require a reception of a synchronizing signal from the display device every switching between a left shutter and a right shutter. This also means that the display device has to transmit the synchronizing signal every opening and closing of the shutters in the eyeglass device. Thus there is a drawback in a highly frequent communication of the synchronizing signal between the display device and the eyeglass device. The highly frequent communication of the synchronizing signal may make a control of the eyeglass device and/or the display device more complicated. Alternatively, the highly frequent communication of the synchronizing signal may also increase a potential interference between the video system and other equipment.